Building heat load reduction method and apparatus

ABSTRACT

A building heat load reduction system is provided having a series of spray nozzles located on a building roof that are connected to a cooling liquid supply. A temperature sensor on the roof is connected to a controller and, depending upon the heat on the roof, supplies liquid coolant to the spray nozzles which sprays the liquid coolant onto the roof. A moisture sensor on the roof or in the roof drain provides a signal to the controller so that once the top of the roof is wet, the sprinkler is shut down so that excess water is not wasted. A liquid coolant/surfactant mixing system is provided which mixes a surfactant with the cooling liquid to provide enhanced cooling. The surfactant causes the liquid coolant being sprayed to have a smaller droplet size which creates a relatively higher specific surface area for the water droplets.

CROSS-REFERENCES TO RELATED APPLICATIONS (if any)

This is a non-provisional application claiming priority of theprovisional application 61/431,995 filed Jan. 12, 2011.

STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY-SPONSOREDRESEARCH AND DEVELOPMENT (IF ANY)

None

BACKGROUND

Heating and cooling costs for commercial buildings are a substantialexpense. In order to use less energy, it would be desirable to find moreefficient ways of heating and/or cooling buildings so that these costsand energy consumption are reduced. During the summer months, coolingrequirements for buildings become very high due to the higher heat load.Typically, additional cooling units or chillers are brought on line inthe summer months to cool buildings. In certain areas energy supplycannot keep up with the demand for energy used in cooling buildingsresulting in rolling brown outs or black outs. This is especially truein the afternoon when the heat load from the sun is the highest,depending upon the building orientation and construction.

The problem of cooling buildings is also more complex due to the varyingheat load by floor based on usage and occupancy. Additionally, thehigher floors of a building require more cooling as the heat within thebuilding structure rises toward the top of the building. So at thebuilding roof, in addition to heat from inside the building rising,there is generally additional heat from direct sunlight making it moredifficult for the building to discharge heat.

It would be desirable to provide a cost efficient method for reducingthe heat load in a building and therefore reduce the amount of coolingrequired.

SUMMARY

Briefly stated, the present invention provides a building heat loadreduction system. The system comprises a series of sprinklers located ona building roof that are connected to a cooling liquid supply. Atemperature sensor on the roof is connected to a controller and,depending upon the heat on the roof, supplies liquid coolant to thesprinkler system which sprays the liquid coolant onto the roof. Amoisture sensor on the roof or in the roof drain provides a signal tothe controller so that once the top of the roof is wet, the sprinkler isshut down so that excess liquid coolant is not wasted. Additionally, aliquid coolant/surfactant mixing system is provided which mixes asurfactant with the cooling liquid to provide enhanced cooling. Thesurfactant concentration can be varied based on temperature. Thesurfactant causes the liquid coolant being sprayed to have a smallerdroplet size which creates a relatively higher specific surface area forthe water droplets. This provides more even coating and allows forbetter heat transfer from the building roof due to more rapidvaporization resulting in enhanced cooling.

In another aspect, a sensor is provided to detect a concentration ofresidual surfactant located on the roof surface. The sensor signals thecontroller to reduce the amount of surfactant being mixed with thecooling liquid prior to spraying based on the residual amount ofsurfactant located on the roof surface.

In another aspect, the invention provides a method for reducing theenergy required for cooling a building. The method includes spraying aliquid coolant on the roof of a building and sensing when liquid reachesthe building roof drain such that the spray of cooling liquid is stoppedso that additional cooling liquid is not wasted. Further, a surfactantsupply and mixing tank is connected to the cooling liquid supply and asurfactant is preferably mixed with the cooling liquid, depending upon aroof temperature of the building, in order to enhance heat transfer fromthe building through more rapid vaporization of the cooling liquid dueto the smaller droplet size and higher specific surface area based onthe surfactant concentration.

In another aspect, the method further includes sensing residualsurfactant on the roof surface activated by the cooling liquid andsignaling the controller so that a concentration of the surfactant addedto the cooling liquid prior to being sprayed onto the building roof isreduced.

Preferably, the cooling liquid is water from the building water supply.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary and the detailed description which follows will bebest understood when read in conjunction with the attached drawings. Inthe drawings:

FIG. 1 is a perspective view showing a portion of a building includingthe roof with a building heat load reduction system according to theinvention located on the roof.

FIG. 2 is an enlarged view of a portion of the sprinkler pipe includingspray nozzles for delivering a cooling liquid to the roof.

FIG. 3 is a schematic diagram showing the cooling liquid mixing andsupply system used in connection with the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Certain terminology is used in the following description for convenienceonly and is not limiting. The words “right,” “left,” “top,” and “bottom”designate directions in the drawings to which reference is made. Thewords “a” and “one” are defined as including one or more of thereferenced item unless specifically stated otherwise. This terminologyincludes the words above specifically mentioned, derivatives thereof,and words of similar import.

Referring to FIG. 1, a building heat load reduction system 10 isschematically illustrated on the roof 14 of a building 12. Such roofs 14typically including HVAC units 16 as well as other building mechanicalsystems which are arranged in various configurations. Accordingly, theillustration shown is meant to be exemplary and the system 10 inaccordance with the invention can be used with other roof topconfigurations.

The roof top portion of the building heat load reduction system includesthe cooling liquid supply pipe 18 which extends up from inside thebuilding 12 where it is connected to a cooling liquid mixing and supplysystem 30, shown schematically in FIG. 1 and explained in further detailbelow in connection with FIG. 3. The cooling liquid supply pipe 18 isconnected to a header pipe 20 which leads to sprinkler pipes 22 a, 22 b,22 c, 22 d which are supported on the roof 14 via supports 24 as shownin FIG. 2. The supports 24 can be A-frames as shown or any othersuitable configuration which keeps the header piper 20 and sprinklerpipes 22 a-d off the roofs surface. Spray nozzles 26 are connected tothe sprinkler pipes 22 a-d and are arranged to provide a pattern forgenerally full coverage of coolant liquid onto the surface of the roof14. In the preferred embodiment, the cooling liquid consists primarilyof water and accordingly, the spray pattern of the nozzles 26 ispreferably arranged to cover substantially all of the roof top. Whileone configuration of the header piper 20 and sprinkler pipes 22 a-d isshown, those skilled in the art will appreciate that various otherconfigurations can be utilized depending upon the roof topconfiguration. Further, it is also possible to provide the header pipe20 and/or the sprinkler pipes 22 a-d directly on the roof top withoutthe supports 24 and the position and angle of the spray nozzles 26 canbe adjusted to still provide full coverage of the roof 14, depending onthe specific roof construction and drainage requirements.

Referring to FIG. 3, the cooling liquid mixing and supply system 30 isshown in detail. The cooling liquid mixing and supply system 30 ispreferably connected to a building water source 32; however, it ispossible to connect it to a source of other type of cooling liquid. Inthe preferred embodiment, the building water source 32 providespressurized water to a control valve 34 which leads to a mixing tank 36.The mixing tank 36 can be an in-line mixing arrangement which usesinternal fins and a venturi effect to mix in a surfactant or can be alarger tank with mixing implements located in the tank, if desired. Thetank outlet 37 of the mixing tank 36 and leads to the cooling liquidsupply pipe 18 that extends to the roof 14 of the building 12.

A surfactant supply tank 46 is also provided and is connected to themixing tank 36 by a surfactant supply line. A pump 38 is located alongthe surfactant supply line and is connected to a controller 50 whichcontrols the pump 38 in order to provide a desired amount of surfactant48 from the surfactant supply tank 46 to the mixing tank 36. Thecontroller 50 is also connected to the control valve 34.

A cooling liquid sensor 40 is located on the roof 14 or in a roof topdrain and is connected to the controller 50. A salinity/surfactantsensor is also located on the roof 14 and is connected to the controller50. Additionally, a temperature sensor 44 is located on the roof 14 andis connected to the controller 50. The controller 50 is preferably a PLCor other computer implemented programmable control.

In use, when the temperature on the roof 14 rises to a predeterminedlevel, the temperature sensor 44 signals the controller 50 which opensthe valve 34 such that pressurized water from the building water source32 is directed to the mixing tank 36. Depending upon the temperature,the pump 38 is activated in order to mix a predetermined amount ofsurfactant 48 into the mixing tank 36 with the water from the buildingwater source 32. The water/surfactant mixture is delivered via the tankoutlet 37 and the cooling liquid supply pipe 18 to the roof topsprinkler system via the header pipe 20 and sprinkler pipes 22 a-d whereit is sprayed via the nozzles 26 onto the roof 14. Depending upon thetemperature, the controller 50 varies the amount of surfactant that ismixed with the water. The specific amount of surfactant will varydepending on the surfactant utilized. The surfactant mixed with thewater results in the spray from the spray nozzles 26 having a smallerdroplet size discharged onto the roof 14. The smaller droplets ofcooling liquid can absorb heat more rapidly due to the larger specificsurface area of the droplets. This promotes heat transfer and more rapidvaporization of the cooling liquid. The water sensor 40 located on theroof 14 or in a roof top drain senses the water spray and determines iftoo much cooling liquid is being sprayed onto the roof and is, forexample, running down the drain. The sensor 40 can be a volumetric flowsensor or a float sensor or any other suitable type of sensor whichdetermines if a sufficient amount of cooling liquid is on the roofsurface or whether cooling liquid is traveling down the roof drain andsignals the controller 50 to close the valve 34 so that additionalcooling liquid is not sprayed on to the roof 14. The heat from thebuilding 12 is transferred to the cooling liquid droplets sprayed ontothe roof 14 which vaporize removing heat from the roof 14 and reducingthe heat load on the building 12.

Various types of surfactants may be utilized in connection with thepresent invention. It is believed that Ecosurf-SH™ or Ecosurf-EH™, whichare available from Dow Chemical may be suitable. It is also possiblethat other types of non-ionic, anionic or cationic surfactants could beutilized.

To the extent that the heat removal from the building causes the waterto evaporate, this results in residual surfactant 14 being left on theroof 14. The residual surfactant can be reactivated via additional watersprayed from the nozzles 26 and reduce the amount of additionalsurfactant which must be mixed with the water delivered from thebuilding water source 32 into the mixing tank 36. Thesalinity/surfactant sensor 42 located on the roof 14 can detect theconcentration of the surfactant in water located on the roof 14 once theroof 14 has been re-wetted. This can help reduce the amount ofadditional surfactant required as well as control the related costs.

The water mixing and supply system 30 can be cycled on and off based onthe temperature sensor 44 as well as the cooling liquid sensor 40 on theroof 14 and/or in the roof drain.

The invention thus provides an economical augmentation to buildingcooling in a simple, cost effective matter.

While the preferred embodiments of the invention have been described indetail above, the invention is not limited to the specific embodimentsdescribed above, which should be considered as merely exemplary. Furthermodifications and extensions of the present invention may be developed,and all such modifications are deemed to be within the scope of thepresent invention as defined by the appended claims.

1. A building heat load reduction system, comprising: a series of spraynozzles located on a building roof that are connected to a coolingliquid supply; a control valve connected between the cooling liquidsupply and the spray nozzles; a temperature sensor on the roof; acontroller, the temperature sensor and the control valve being connectedto the controller such that depending upon a temperature of the roof,the controller opens the control valve to supply liquid coolant to thespray nozzles which spray the liquid coolant onto the roof; a liquidsensor on the roof or in a roof drain and connected to the controller toprovide a signal to the controller so that once a predetermined amountof cooling liquid is on the roof, the controller closes the controlvalve.
 2. The building heat load reduction system according to claim 1,further comprising a liquid coolant/surfactant mixing system locatedbetween the control valve and the spray nozzles that mixes a surfactantwith the cooling liquid to provide enhanced cooling.
 3. The buildingheat load reduction system according to claim 1, further comprisingwhere said liquid coolant is water.
 4. The building heat load reductionsystem according to claim 1, further comprising where said liquidcoolant is a mixture of water and one or more surfactant.
 5. Thebuilding heat load reduction system according to claim 1, furthercomprising having a salinity/surfactant sensor located on the roof todetect the concentration of the surfactant in water located on the roofonce the roof has been re-wetted.
 6. The building heat load reductionsystem according to claim 5, further comprising having the residualsurfactant be reactivated by the additional liquid sprayed from thespray nozzles.
 7. The building heat load reduction system according toclaim 2, further comprising having with the water delivered from thebuilding water source into said mixing system.
 8. The building heat loadreduction system according to claim 2, further comprising having saidmixing system being a mixing tank.
 9. The building heat load reductionsystem according to claim 8, further comprising having said mixing tankbeing an in-line mixing arrangement which uses internal fins and aventuri effect.
 10. The building heat load reduction system according toclaim 8, further comprising having said mixing tank having mixingimplements located in the tank.
 11. The building heat load reductionsystem according to claim 8, further comprising having a tank outletfrom the mixing tank that leads to the cooling liquid supply pipe. 12.The building heat load reduction system according to claim 8, furthercomprising having a surfactant supply tank connected to the mixing tankby a surfactant supply line.
 13. The building heat load reduction systemaccording to claim 12, further comprising having a pump located alongthe surfactant supply line and connected to the controller.
 14. Thebuilding heat load reduction system according to claim 13, furthercomprising having the controller controlling the pump to provide adesired amount of surfactant from the surfactant supply tank to themixing tank.
 15. The building heat load reduction system according toclaim 1, further comprising having the liquid sensor being a volumetricflow sensor.
 16. The building heat load reduction system according toclaim 1, further comprising having the liquid sensor being a floatsensor.
 17. The building heat load reduction system according to claim1, further comprising having the spray nozzles and the cooling liquidsupply being supported by supports.
 18. The building heat load reductionsystem according to claim 17, further comprising having said supportsbeing A-frames.
 19. The building heat load reduction system according toclaim 1, further comprising having the spray nozzles arranged in apattern that fully covers the roof with said coolant.
 20. The buildingheat load reduction system according to claim 1, further comprisinghaving the heat from the building transferred to the cooling liquiddroplets sprayed onto the roof causing said liquid droplets to vaporizeremoving heat from the roof and reducing the heat load on the building.